The correct answer to the question: What did the Clean Air Act allow citizens to do that no previous U.S. environmental law had allowed, would be: it was the first law that considered citizen lawsuits against the correct enforcement of the statutes stated in the Act.
Explanation:
The Clean Air Act, which was passed originally in 1963, and which has been amended since, with its last update being in the 1990´s, became the first time that the U.S government not only established federal funding for environmental issues, but also regulated environmental topics through EPA (Environmental Protection Agency, 1970) and considered the power that citizens could have to ensure the enforcement of the statutes and provisions considered in the Act. This consideration of citizen suits, is the most important and relevant difference with earlier environmental laws.
